Internal line replaceable unit high intensity radiated field detector

ABSTRACT

Various embodiments for detecting a High Intensity Radiated Field (HIRF) in a Line Replaceable Unit (LRU) are provided. The internal detector may be used to test EMI filter pin connectors of a closed LRU. For example, a method comprises setting a selecting switch to a test connector position, thereby connecting a RF signal generator to a testing connection cable. The method further comprises causing the generator to generate a test signal as input into the testing connection cable, and determining if an internal HIRF detector has detected the signal. If the signal is detected, the method further comprises, for each EMI filter pin connector in the LRU, switching the selecting switch to a corresponding test cable coupled to an EMI filter pin connector, causing the generator to generate the test signal as input into the corresponding test cable; and determining if the detector has detected the signal.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.13/455,777, filed Apr. 25, 2012, the entire contents of which areincorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to the detection of High Intensity RadiatedFields (HIRF). More particularly, this invention relates to a detectorfor detecting HIRF in a line replaceable unit.

BACKGROUND

Line Replaceable Units (LRU) are used in commercial and militaryapplications to provide a specific function. A line replaceable unitincludes chassis and a plurality of electronic circuits. Some of theelectronic components that form the electronic circuits may be sensitiveto HIRF. At some level of HIRF intensity a circuit may malfunctioncausing the LRU to malfunction. A typical LRU has ElectromagneticInterference (EMI) protection such as EMI filter pins in the LRUconnectors used to connect the LRU to external cabling and carefulshielding of the chassis covers. These protection elements, however, canfail, resulting in the electronic components being subject to the HIRF.

LRUs are tested after assembly to verify that their operation meetsspecification in an Acceptance Test using factory Test Equipment. In asimilar manner, LRUs that have failed and are repaired in the factory orin a test facility are tested to a similar specification using thefactory Test Equipment or other test equipment that can accomplish thesame testing. These tests are referred to as Continued Airworthinesstests in the case of equipment used on Civil Aircraft.

The testing is conducted on a closed box. That is; the unit is connectedto test equipment using cabling similar to that in the vehicle withloads and inputs which simulate normal interfaces.

SUMMARY OF THE INVENTION

Accordingly, disclosed is a system, device and method for verifying theintegrity of the EMI filter pin connectors or LRU shielding in a closedLRU.

Disclosed is a Line Replaceable Unit (LRU) comprising at least onecircuit board, each of the at least one circuit board comprising circuitcomponents mounted thereto and circuit traces, a chassis; a built-intest section; an external connector having a EMI filter; and an internalHigh Intensity Radiated Field (HIRF) detector. The detector comprises areceiving means for receiving HIRF and generating an Alternating Current(AC) signal proportional to the HIRF, an RF filter configured to samplethe AC signal to create a Direct Current (DC) signal; and a detectingsection configured to compare the DC signal with a threshold and outputa result of the comparison to the built-in test section.

Also disclosed is a High Intensity Radiated Field (HIRF) detectorinstalled in a line replaceable unit comprising a receiving means forreceiving HIRF and generating an AC signal proportional to the HIRF, anRF filter configured to sample the AC signal to create a DC signal; anda detecting section configured to compare the DC signal with a thresholdand output a result of the comparison to a built-in test section.

Also disclosed is a method for testing EMI filter pin connectors of aclosed line replaceable unit comprising setting a selecting switch to aTest Connector position, thereby connecting a RF signal generator to atesting connection cable, the testing connection cable being attached toa Test Connector of a line replaceable unit, causing the RF signalgenerator to generate a test signal as input into the testing connectioncable; determining if a detector has detected the test signal. If thetest signal is detected, the method further comprises, for each EMIfilter pin connector in the line replaceable unit, switching theselecting switch to a corresponding test cable coupled to an EMI filterpin connector, causing the RF signal generator to generate the testsignal as input into the corresponding test cable and determining if thedetector has detected the test signal, wherein if the test signal isdetected, the associated EMI filter pin connector coupled to the testcable is not functioning properly.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, benefits, and advantages of the presentinvention will become apparent by reference to the following figures,with like reference numbers referring to like structures across theviews, wherein:

FIG. 1 illustrates a block diagram of an example of an internal detectorin accordance with the invention;

FIGS. 2A and 2B illustrate high level schematics of examples of theReceiving Section in accordance with the invention;

FIG. 3 illustrates an example of a circuit board having the antennatrace according to an embodiment of the invention;

FIG. 4 illustrates a block diagram of the Processing Section inaccordance with the invention;

FIG. 5A illustrates a schematic diagram of an example of an internaldetector in accordance with the invention.

FIG. 5B illustrates test results for the example internal detectordepicted in FIG. 5A.

FIG. 6A illustrate an external view of LRU, FIG. 6B illustrates anexplode view of an LRU and FIG. 6C illustrate an external view of theLRU showing EMI filter pin connector slots and a Test Connector.

FIG. 7 illustrates a flow chart for a method of testing the EMI filterpin connectors and chassis shielding during acceptance testing; and

FIG. 8 illustrates a diagram of an example of an acceptance Test andContinuous Airworthiness Testing systems for testing the EMI filter pinconnectors for a LRU in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION Definitions

Line Replaceable Unit (LRU) is a modular component used in the militaryand commercial industries that is designed to be replaced quickly at adefined location. LRUs are designed to be removed and replaced on theflight line, hence the term “Line” Replaceable Unit.

FIG. 1 illustrates a block diagram of an internal High IntensityRadiated Fields (HIRF) detector 100. The HIRF environment is applicableto equipment that is subject to extreme electromagnetic environmentsand/or mission critical equipment whose failure would be hazardous tohuman safety. As greater dependence is placed upon a vehicle'selectrical and electronic systems performing functions required for safeoperations, concern has increased for the protection of these systems.Concern for the protection of electrical and electronic systems inaircraft and other vehicles has increased substantially in recent yearsdue to:

-   -   Reduction in the electromagnetic shielding afforded by new        composite materials.    -   Increased use of electrical and electronic systems in aircraft        for flight/landing systems and in ground vehicles for propulsion        and control systems.    -   Increased susceptibility of systems to HIRF due to increased        data bus and processor operating speeds, higher density        integrated circuits and cards, and greater sensitivities of        electronic equipment.    -   Expansion of frequency usage above 1 GHz.    -   Increasing severity of HIRF environment because of an increase        in the number of RF transmitters.

HIRF requirements are applied to ensure that the electrical andelectronic systems are able to continue safe operation withoutinterruption, failure or malfunction, including those in LRUs.

The internal detector 100 is configured to detect HIRF (“HIRFDetector”). The HIRF Detector 100 includes a Receiving Section 105, a RFAmplifier 110, a RF Detector/Filter 120, and a Processing Section 125.The Receiving Section 105 is coupled to a RF Amplifier 110. The RFAmplifier 110 is coupled the RF Detector/Filter 120. The ProcessingSection 125 is coupled to RF Detector/Filter 120. The RF Amplifier 110,the RF Detector/Filter 120 and Processing Section 125 are mounted on oneor more Printed Wire Boards. In one embodiment, the RF Amplifier 110,the RF Detector/Filter 120 and Processing Section 125 are mounted to thesame Printed Wire Board.

The Receiving Section 105 is designed to a predetermined frequencyrange. For example, the frequency range can be 100 MHz to 1 GHz.However, the design frequency range can be application specific, e.g.,different for different types of LRUs. The Receiving Section 105 will bedescribed in detailed with respect to FIGS. 2A and 2B.

The gain of the RF Amplifier 110 can be set to account for the ambientnoise caused the internal electronic components. Additionally, the gainof the RF Amplifier 110 is determined based upon the preset detectionthreshold stored in the Processing Section 125. Although, the RFAmplifier 110 is depicted in the diagram (FIG. 1), the RF Amplifier 110is optional and may not be needed in all applications. The RFDetector/Filter 120 can be a circuit containing a detection diode D1 anda RC filter section as depicted in FIG. 5A.

In an embodiment, the Processing Section 125 can be programmed with twomodes: a testing mode and a continuous operation mode. In the testingmode, the Processing Section 125 can output the detection bit to anexternal device and in the continuous operation mode, the ProcessingSection 125 outputs the detection bit to the internal built-in testsection.

FIG. 1 depicts both the test input (test signal in testing mode) and theHIRF signal (continuous operation mode) as inputs to the ReceivingSection 105. Additionally, FIG. 1 depicts both the bit detection signaloutput to the built-in test section (continuous operation mode) and tothe Test Connector 630 (as depicted in FIGS. 6C and 8, in testing mode).

The elements of the HIRF Detector 100 can be powered from an LRU powersupply, if needed. For example, the RF Amplifier 110 can be biased usingthe LRU power supply.

FIG. 2A illustrates an example of a Receiving Section 105A. TheReceiving Section 105A comprises the Receiving Elements 200, such as anantenna array, coupling wire(s), antenna traces 310. The ReceivingElement(s) 200 can be one or more antenna wires mounted or attached tothe chassis, mounted along the chassis walls in a three-dimensionalorientation, a circuit trace embedded or etched into a Printed WireBoard Layer 305 of a Printed Wire Board (module) 300 or one or more ofthe coupling wires between two Printed Wire Boards 300. FIG. 3illustrates an example of Antenna Trace 310 routed along side ofinternal wiring from the external connectors to the mother board. Oneend of the Antenna Trace 310 is coupled to the Summing Element 205(Receiving Section 105A) or Multiplexer 215 (Receiving Section 105B).

Additionally, if the Receiving Element(s) 200 is an antenna wire mountedto the chassis, a plurality of metallic wires can be used to create a3-dimensional mapping to generate signals representative of the fieldsin the x, y, and z directions. The signals are then combined to detectthe HIRF.

In an embodiment, antenna traces 310 can be added to each Printed WireBoard 300 of an LRU. Therefore, even if the HIRF field is uneventhroughout the inside of the LRU, a HIRF level high enough to cause aLRU response can be detected.

The Receiving Section 105 can be located in proximity to the EMI filterpin connectors 625 (an example of the EMI filter pin connectors aredepicted in FIGS. 6C and 8). For example, in an embodiment, theReceiving Section 105 can be an antenna trace 310 embedded in theclosest Printed Wire Board 300. Additionally, the Receiving Section 105can be mounted on the chassis near the EMI filter pin connectors.Alternatively, the Receiving Section 105 can be located in proximity tosensitive circuit components to measure the HIRF near the sensitivecomponents such as analog circuits and high gain circuits.

The Receiving Section 105A further comprises a summing element (Σ) 205for adding the signals received from each of the Receiving Element(s)200 and a Buffer 210 for buffering the added signals. The ReceivingSection 105A output is an added signal to the RF Amplifier 110.

FIG. 2B illustrates an example of another Receiving Section 105B. TheReceiving Section 105B comprises the same Receiving Elements 200,however, instead of adding all of the received signals, the receivedsignals are selected one at a time by a Multiplexer 215. Each selectedsignal is successively buffered by Buffer 210. The Multiplexer 215repeatedly outputs one selected signal at a time to the Buffer 210. Eachsignal received from the Receiving Elements 200 is selectively outputfor each cycle. The Receiving Section 105B outputs the currentlyselected signal to the RF Amplifier 110. Receiving Section 105B allowsfor each signal to be examined by the Processing Section 125.

FIG. 4 illustrates a block diagram depicting an example of theProcessing Section 125. In the example of the Processing Section 125depicted in FIG. 4, the Processing Section 125 comprises a Comparator400, a Sampler 405 and a Persistence Detector 410. In an embodiment, theProcessing Section 125 includes a storage device (not shown) for storingat least one detection threshold. Since each LRU reacts differently to aHIRF, the detection threshold varies based on the type of LRU and theelectronic components mounted to the print wire boards 300. Thereforethe detection threshold can be application specific. The detectionthreshold also can be remotely adjusted after assembly, as necessary. Inthis embodiment, the storage device may also include a thresholdadjustment for performing the functionality described herein.

The Processing Section 125 receives the output of the RF Detector/Filter120 (showing in FIG. 4 as input) and the Comparator 400 compares thisinput with the detection threshold. If the received output is higherthan the detection threshold, the Comparator 400 outputs a signalindicating a positive detection to the Sampler 405. For example, theComparator 400 can output a “high” signal value. If the input is lessthan the detection threshold, the Comparator 400 outputs a signalindicating a negative detection to the Sampler 405. For example, theComparator 400 can output a “low” signal value.

The Sampler 405 periodically samples the output of the Comparator 400.The sample rate is preset. The sample rate can be every 30 seconds.However, the sample rate can be application specific. Furthermore, in anembodiment, the sample rate can be remotely adjusted after assembly, asnecessary. In this embodiment, the storage device (not shown) may alsoinclude a sample rate adjustment for performing the functionalitydescribed herein. If the Sampler 405 receives a positive detectionsignal during the sample period, e.g., a “high” signal, the Sampler 405outputs a positive detection signal to the Persistence Detector 410. Ifthe Sampler 405 receives a negative detection signal during the sampleperiod, e.g., a “low” signal, the Sampler 405 outputs a negativedetection signal to the Persistence Detector 410.

The Persistence Detector 410 is configured to determine if the positivedetection signal received from the Sampler 405 occurs for a period oftime where the HIRF signal can cause damage. In an embodiment, thePersistence Detector 410 counts the number of consecutive positivedetection signals received from the Sampler 405 and compares the countednumber with a threshold. If the counted number is greater than thethreshold, the Persistence Detector 410 outputs a positive detection bitto the built-in test section (in continuous operation mode) or to theTest Connector 630 (in testing mode). The built-in test section can bemounted on the same Printed Wire Board 300. In another embodiment, thePersistence Detector 410 counts the number of positive detection signalsreceived from the Sampler 405 within a preset period of time. If thecounted number is greater than the threshold, the Persistence Detector410 outputs a positive detection bit to the built-in test section or theTest Connector 630. In another embodiment, the Persistence Detector 410tracks the number of positive detection signals received in a period oftime and the number of negative detection signals received within thesame period of time. The Persistence Detector 410 separately adds thenumber of positive detection signals and the negative detection signalsand then subtracts the total number of negative detection signals fromthe total number of positive detection signals to obtain a net positivedetection value. If the net positive detection value is greater than thethreshold, the Persistence Detector 410 outputs a positive detection bitto the built-in test section (or the Test Connector 630).

While FIG. 4 depicts the Comparator 400, Sampler 405 and the PersistenceDetector 410 separately, these components can be integrated into asingle processor. The processor can be a microprocessor or a CPU.Additionally, the functionality of the Comparator 400, Sampler 405 andpersistence detection 410 can be implemented using a Programmable ArrayLogic (PAL), Programmable Logic Device (PLD), Field Programmable ArrayLogic (FPGA) or an Application Specific Integrated Circuit (ASIC).

The Processing Section 125 is powered from the LRU Power Supply (notshown).

The HIRF Detector 100 can be used during initial testing, such asacceptance testing, during continuous operation and during maintenanceprocedure such as continued airworthiness (CAW) tests.

FIG. 5A illustrates a schematic diagram of an example of HIRF Detector100. FIG. 5B depicts simulated and measured test results for thisdetector. A signal having a known signal strength was input. The outputvoltage was measured using a voltmeter. The simulated resultssubstantially correlate with the measure voltages. As can be seen fromFIG. 5B, the frequency response for the detector is relatively flat overmeasured frequency range.

FIG. 6A illustrates an external view of an example of an LRU 600. FIG.6A depicts the external chassis shielding 605. FIG. 6B illustrates anexternal exploded view of the same LRU 600. The external viewillustrates multiple Printed Wire Boards 300. The front panel 610 andrear panel assembly 615 and the side panels 620 form a housing for thePrinted Wire Boards 300. The front panel 610, rear panel assembly 615,and side panels 620 collectively form the chassis shielding 605. ThePrinted Wire Boards 300 attached to slots in the rear panel assembly615.

FIG. 6C illustrates an external view of a second example of an LRU 600A.A panel comprises a plurality of EMI filter pin connectors 625 and aTest Connector 630. During testing, the Test Connector 630 is coveredwith a metallic cover 635.

The HIRF Detector 100 is sensitive to higher than normal intruding EMIfields from external sources. Each LRU 600 also includes a built-in testsection (not shown).

Each Printed Wire Board 300 has electronic component mounted thereto.These electronic components are configured to perform the functionalityof the LRU, e.g., LRU 600. Additionally, according to certain aspects ofthe invention, one or more of the Printed Wire Boards 300 also includeselectronic components that are dedicated to detect HIRF and output asignal to a built-in test section. If a HIRF is detected, there is ahigh likelihood that either one of the EMI filter pin connectors 625and/or the chassis shielding 605 have failed. The HIRF Detector 100provides a closed-box testing.

A typical LRU, e.g., LRU 600, is tested using an extensive qualificationand acceptance testing that exposes the units and a model of theirinterconnections cabling to high amounts of electromagnetic energy (RFenergy), representative of a real world exposures that the units can andwill be exposed during service. The tests use various test equipment toevaluate the levels of energy and the response of the unit.

The test implements an Acceptance Test Procedure (ATP)/ContinuousAirworthiness Procedure. The tests are required to be performed with theLRUs 600 closed and in a ready-for-delivery configuration. The HIRFDetector 100 is used to determine the integrity of the LRU 600 relatedto an exposure of the RF energy.

FIGS. 7 and 8 illustrate the testing procedure and test setup,respectively.

The test setup 800 comprises an external test RF Signal Generator 805, aConnector Switch 810, a plurality of External Test Cables 815 _(N) and aTest Connector 630. The Connector Switch 810 comprises a plurality ofswitching positions and will selectively couple the test signalgenerated by the RF Signal Generator 805 to each of the External TestCable 815 and the Test Connector 630 via the connector testing cable631. As depicted in FIG. 8, the Connector Switch 810 has four switchpositions (illustrates by the dots). Three of the switching positionsare used to couple the three External Test Cables 815 (three EMI filterpin connectors 625 _(N)) to the RF Signal Generator 805. One of theswitching positions is used to couple the Test Connector 630 to the RFSignal Generator 805. The Connector Switch 810 will need to have onemore switching position than the number of EMI filter pin connectors 625_(N). Each EMI filter pin connector 625 has a corresponding ExternalTest Cable 815 coupled to it. As depicted, there are three EMI filterpin connectors 625 ₁₋₃ and three external test cables 815 ₁₋₃. FIG. 8illustrates a portion of the External Test Cable being exposed to showthe internal test cable wires and the coupling resistors (test cablewires 816). The External Test Cables 815 ₁₋₃ have LRU connectors at oneend and at the other end each wire in the cable is terminated in acoupling resistor. The other terminal of each of the isolation resistorsassociated with a given cable is connected together and connected to theoutput amplifier. Each external test cable 815 is similarly fitted.

The Test Connector 630 is coupled to the internal HIRF Detector 100. TheTest Connector 630 is not fitted with EMI filters. When not in use, thearea where the Test Connector 630 is located is capped with the metalliccover 635 for EMI shielding. The Test Connector 630 is capped duringtesting to present the test frequency signal being leaked into the LRU,e.g., 600A.

The output of the internal HIRF Detector 100 is sent to a test equipmentcomputer (the computer is not shown in FIG. 8). However, the output ofthe internal HIRF Detector 100 is illustrated as Detection Signal 830.

As depicted in FIG. 8, the LRU under test, e.g., LRU 600A, comprisesthree internal circuit modules (wire boards 300 ₁₋₃), three EMI filterpin connectors 625 ₁₋₃ and a rear panel assembly 615. The EMI filter pinconnectors 625 ₁₋₃ are coupled to the rear panel assembly 615 via cables817 ₁₋₃.

FIG. 7 illustrates a flow chart of an example of a testing method. Thetesting method will be described in conjunction with the test setupdepicted in FIG. 8. However, the testing method is not limited to thetest setup 800 depicted in FIG. 8 and can be conducted using othertesting setups.

At step 700, the Connector Switch 810 is set to the Test Connector 630,which couples the RF Signal Generator 805 to the Test Connector 630. Atstep 705, the LRU, e.g., 600A having the internal HIRF Detector 100, isexcited with the test frequency signal the internal HIRF Detector can beon one or more of the Internal Circuit Modules 300 ₁₋₃ (Printed WireBoard). The power level of the test frequency signal is predeterminedand controlled. The RF Signal Generator 805 is set to the predeterminedfrequency and amplitude for the Test Connector input. At step 710, theProcessing Section 125 compares the output of RF Filter/Detector 120with the preset threshold. The Processing Section 125 compares a digitalvalue of the test frequency signal with the preset threshold. Thedigital value is generated from the received test frequency signal. TheHIRF Detector 100 should indicate that HIRF has been detected. At step715, a determination is made if the HIRF Detector 100 detected the HIRFby evaluating the Detection Signal 830 on the test equipment computer.If the HIRF Detector 100 detected the HIRF, then the testing proceeds(“Y” at step 715). This test validates that the HIRF Detector 100functions properly.

At step 720, the Connector Switch 810 is set to one of the External TestCables, e.g., 815 ₁, which couples the RF Signal Generator 805 to theexternal test cables 815 ₁. For each external test cable 815, the LRUwith the internal HIRF Detector 100 is excited with the test frequencysignal at step 725. At step 730, the Processing Section 125 compares theoutput of RF Filter/Detector 120 with the preset threshold. At step 730,the Processing Section 125 outputs the Detection Signal 830. At step735, a determination is made if the HIRF Detector 100 detected the HIRFby evaluating the Detection Signal 830 on the test equipment computer.If all of the EMI filter pin connectors 625 are functioning properly noresponse from the HIRF Detector 100 is expected (“N” at step 735). Ifthe HIRF Detector 100 registers a HIRF intrusion, the EMI filter pinconnector 625 is faulty (“Y” at step 735) and must be replaced orrepaired (step 737).

Steps 720-735 are repeated for each EMI filter pin connection 625. Afterstep 735, a determination is made if there are any untested EMI filterpin connectors 625 (step 740). If there are untested EMI filter pinconnectors (“Y” at step 440), the process returns to step 720. If not,(“N” at step 740), the process is done and all of the EMI filter pinconnectors 625 are functioning properly (step 742).

If at step 715, the test signal is not detected by the HIRF Detector100, the HIRF Detector 100 is faulty (“N” at step 715) and should beexamined for further evaluation (step 717).

Various aspects of the present disclosure may be embodied as a program,software, or computer instructions embodied or stored in a computer ormachine usable or readable medium, which causes the computer or machineto perform the method when executed on the computer, processor, and/ormachine. A computer readable medium, tangibly embodying a program ofinstructions executable by the machine to perform variousfunctionalities and methods described in the present disclosure is alsoprovided.

The computer readable medium could be a computer readable storage mediumor a computer readable signal medium. Regarding a computer readablestorage medium, it may be, for example, a magnetic, optical, electronic,electromagnetic, infrared, or semiconductor system, apparatus, ordevice, or any suitable combination of the foregoing; however, thecomputer readable storage medium is not limited to these examples.Additional particular examples of the computer readable storage mediumcan include: a portable computer diskette, a hard disk, a magneticstorage device, a portable Compact Disc Read-Only Memory (CD-ROM), aRandom Access Memory (RAM), a Read-Only Memory (ROM), an ErasableProgrammable Read-Only Memory (EPROM or Flash memory), an electricalconnection having one or more wires, an optical fiber, an opticalstorage device, or any appropriate combination of the foregoing;however, the computer readable storage medium is also not limited tothese examples. Any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device could be a computer readable storage medium.

The computer instructions may be provided to a processor of a generalpurpose computer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor of the computer or other programmabledata processing apparatus, create means, devices, units, or sections forimplementing the functionality specified.

The Detector may be any type of known or will be known systems such as,but not limited to, a virtual computer system and may typically includea processor, memory device, a storage device, input/output devices,internal buses, and/or a communications interface for communicating withother computer systems in conjunction with communication hardware andsoftware, etc.

The terms “element”, “interface”, “section”, “device” or “unit” as maybe used in the present disclosure may include a variety of combinationsof fixed and/or portable computer hardware, software, peripherals, andstorage devices. The Detector or system may include a plurality ofindividual components that are networked or otherwise linked to performcollaboratively, or may include one or more stand-alone components.

The function(s) described herein may occur out of the order noted in thefigures or text including in the reverse order or concurrently (orsubstantially concurrently) depending upon the functionality involved.

The embodiments described above are illustrative examples and it shouldnot be construed that the present invention is limited to theseparticular embodiments. Thus, various changes and modifications may beeffected by one skilled in the art without departing from the spirit orscope of the invention as defined in the appended claims.

What is claimed is:
 1. A method for testing EMI filter pin connectors ofa closed line replaceable unit comprising: setting a selecting switch toa test connector position, thereby connecting a RF signal generator to atesting connection cable, the testing connection cable being attached toa test connector of a line replaceable unit; causing the RF signalgenerator to generate a test signal as input into the testing connectioncable; determining if an internal high intensity radiated field detectorhas detected the test signal, wherein if the test signal is detected,the method further comprises, for each EMI filter pin connector in theline replaceable unit, switching the selecting switch to a correspondingtest cable coupled to an EMI filter pin connector; causing the RF signalgenerator to generate the test signal as input into the correspondingtest cable; and determining if the detector has detected the testsignal, wherein if the test signal is detected, the associated EMIfilter pin connector coupled to the test cable is not functioningproperly.
 2. The method for testing EMI filter pin connectors of aclosed line replaceable unit according to claim 1, wherein when the RFsignal generator generates the test signal as input into the testingconnection cable, if the test signal is not detected by the internalhigh intensity radiated field detector, the internal high intensityradiated field detector is determined to be not functioning properly. 3.The method for testing EMI filter pin connectors of a closed linereplaceable unit according to claim 1, wherein the test connector of theline replaceable unit does not have an EMI filter.